Aggregation of Plug-in Electric Vehicles in Power Systems for Primary Frequency Control

The number of plug-in electric vehicles (PEVs) is likely to increase in the near future and these vehicles will probably be connected to the electric grid most of the day time. PEVs are interesting options to provide a wide variety of services such as primary frequency control (PFC), because they are able to quickly control their active power using electronic power converters. However, to evaluate the impact of PEVs on PFC, one should either carry out complex and time consuming simulation involving a large number of PEVs or formulate and develop aggregate models which could efficiently reduce simulation complexity and time while maintaining accuracy. This thesis proposes aggregate models of PEVs for PFC. The final aggregate model has been developed gradually through the following steps. First of all, an aggregate model of PEVs for the PFC has been developed where various technical characteristics of PEVs such as operating modes (i.e., idle, disconnected, and charging) and PEV’s state of charge have been formulated and incorporated. Secondly, some technical characteristics of distribution networks have been added to the previous aggregate model of PEVs for the PFC. For this purpose, the power consumed in the network during PFC as well as the maximum allowed current of the lines and transformers have been taken into account. Thirdly, the frequency stability margins of power systems including PEVs have been evaluated and a strategy to design the frequency-droop controller of PEVs for PFC has been described. The controller designed guaranties similar stability margins, in the worst case scenario, to those of the system without PEVs. Finally, a method to evaluate the positive economic impact of PEVs participation in PFC has been proposed.En el futuro cercano se espera un notable incremento en el número de vehículos eléctricos enchufables (PEVs), los cuales están conectados a la red eléctrica durante la mayor parte del día. Los PEVs constituyen una opción interesante a la hora de proporcionar una amplia variedad de servicios, tales como el control primario de frecuencia (PFC), dado que tienen la capacidad de controlar rápidamente el flujo de potencia activa a través de convertidores electrónicos de potencia. Sin embargo, para evaluar el impacto de los PEVs sobre el PFC se debe llevar a cabo una simulación computacionalmente compleja y con un largo tiempo de simulación en la que se considere un gran número de PEVs. Otra opción sería la formulación y desarrollo de modelos agregados, los cuales podrían reducer eficazmente la complejidad y tiempo de simulación manteniendo una alta precisión. Esta tesis propone modelos agregados de PEVs para PFC. El modelo agregado definitivo ha sido desarrollado de manera gradual a través de los siguientes pasos. En primer lugar, se ha desarrollado un modelo agregado de PEVs para PFC en el cual son incorporadas varias características técnicas de los PEVs, tales como los modos de operación (inactivo, desconectado y cargando), y la formulación del estado de carga de los PEVs. En segundo lugar, ciertas características técnicas de las redes de distribución han sido consideradas en el modelo agregado de PEVs para PFC previamente propuesto. Para este fin, la potencia consumida por la red durante el PFC, así como la corriente máxima permitida en las líneas y transformadores han sido consideradas. En tercer lugar, se han evaluado los márgenes de estabilidad en la frecuencia de los sistemas de potencia que incluyen PEVs y se ha descrito una estrategia para diseñar un control de frecuencia-droop de PEVs para PFC. El controlador diseñado garantiza márgenes de estabilidad similares, en el peor de los casos, a aquellos de un sistema sin PEVs. Finalmente, se ha propuesto un método para evaluar el impacto económico positivo de la participación de los PEVs en el PFC.Inom en snar framtid förväntas antalet laddbara bilar (laddbilar) öka kraftig, vilka tidvis kommer att vara anslutna till elnätet. Då laddbilar snabbt kan styra och variera sin aktiva laddningseffekt med hjälp av kraftelektroniken i omriktaren kan dessa fordon erbjuda en rad systemtjänster, såsom primär frekvensregleringen. Att utvärdera hur laddbilarna kan påverka den primära frekvensreglering är utmanande då en stor mängd laddbilar måste beaktas vilket kräver komplexa och tidskrävande simuleringar. Ett effektivt sätt att minska komplexiteten men bibehålla noggrannheten är genom att utforma och använda aggregerade modeller. Syftet med denna avhandling är att ta fram aggregerade modeller för laddbilars påverkan på primär frekvensreglering. Modellen har gradvis utvecklats genom följande steg. I första steget har en aggregerad modell av hur laddbilar kan användas för primär frekvensreglering utvecklats där olika tekniska detaljer så som laddbilars tillstånd (d.v.s. inkopplade, urkopplade eller laddas) och laddningnivån beaktats. I andra steget har en modell av distributionsnätet integrerats i den aggregerade modellen. Här tas hänsyn till effektflöden i elnätet samt begränsningar i överföringskapacitet i transformatorer och ledningar i distributionsnätet. I ett tredje steg har frekvensstabiliteten i ett elnät med laddbilar utvärderats och en strategi för hur en frekvensregulator kan designas för att tillhandahålla primär frekvensreglering med hjälp av laddbilar har utvecklats. Designen garanterar samma stabilitetsmarginal för styrsystemet både med och utan laddbilar. Dessutom föreslås en metod för att utvärdera de ekonomiska effekterna av att använda laddbilar för primär frekvensreglering.  Het aantal elektrische voertuigen (EV’s) zal zeer waarschijnlijk toenemen in de nabije toekomst en deze voertuigen zullen vermoedelijk gedurende het grootste deel van de dag aan het elektriciteitsnetwerk aangesloten zijn. EV’s zijn interessante opties om een grote verscheidenheid van diensten te leveren, zoals bijvoorbeeld primaire frequentieregeling, omdat ze snel hun actieve vermogen kunnen aanpassen met behulp van elektronische vermogensomvormers. Echter, om de invloed van EV’s en primaire frequentieregeling te kunnen evalueren, moet men complexe en tijdrovende simulaties met een groot aantal EVs uitvoeren of verzamelmodellen formuleren en ontwikkelen die de complexiteit en duur van de simulaties kunnen reduceren zonder nauwkeurigheid te verliezen. Dit onderzoek presenteert verzamelmodellen voor EV’s en primaire frequentieregeling. Het uiteindelijke verzamelmodel is geleidelijk ontwikkeld door de volgende stappen te nemen. Ten eerste is een verzamelmodel voor EV’s en primaire frequentieregeling ontwikkeld waar verscheidene technische karakteristieken van EV’s, zoals bedieningsmodi (bijv. Inactief, losgekoppeld en ladend) en de actuele laadtoestand in zijn geformuleerd en geïntegreerd. Ten tweede zijn enkele technische karakteristieken van distributienetwerken toegevoegd aan het eerdere verzamelmodel van EV’s voor primaire frequentieregeling. Hiervoor zijn de vermogensconsumptie in het network gedurende primaire frequentieregeling en de maximaal toegestane stroomsterkte van de kabels meegerekend. Ten derde zijn de marges voor de frequentiestabiliteit van elektriciteitssystemen met EV’s geëvalueerd en is een strategie voor het ontwerpen van de frequentie-droop regeling van de EV’s voor primaire frequentieregeling beschreven. De ontworpen controller garandeert soortgelijke stabiliteitsmarges in het slechtste scenario, als voor het systeem zonder EV’s. Ten slotte is er een methode voorgesteld om de positieve economische invloed van EV-participatie in primaire frequentieregeling te evaluëren.“SETS Joint Doctorate ProgrammeThe Erasmus Mundus Joint Doctorate in Sustainable Energy Technologies and Strategies (SETS), the SETS Joint Doctorate, is an international programme run by six institutions in cooperation:• Comillas Pontifical University, Madrid, Spain• Delft University of Technology, Delft, the Netherlands• Florence School of Regulation, Florence, Italy• Johns Hopkins University, Baltimore, USA• KTH Royal Institute of Technology, Stockholm, Sweden• University Paris-Sud 11, Paris, FranceThe Doctoral Degrees provided upon completion of the programme are issued by Comillas Pontifical University, Delft University of Technology, and KTH Royal Institute of Technology.The Degree Certificates are giving reference to the joint programme. The doctoral candidates are jointly supervised, and must pass a joint examination procedure set up by the three institutions issuing the degrees.This Thesis is a part of the examination for the doctoral degree.The invested degrees are official in Spain, the Netherlands and Sweden respectively.SETS Joint Doctorate was awarded the Erasmus Mundus excellence label by the European Commission in year 2010, and the European Commission’s Education, Audiovisual and Culture Executive Agency, EACEA, has supported the funding of this programmeThe EACEA is not to be held responsible for contents of the Thesis.”  QC 20170412</p

School counselor's role in crime prevention work : A qualitative study on the prevention and remedial work of counselors in schools against juvenile delinquency

Juvenile delinquency is a well known problematic issue in today's society, it is a social phenomenon that can jeopardize children and youths futures. Juvenile delinquency can lead to social problems and therefore is the prevention work crucial for children and youths that are affected by the matter. Previous research about juvenile delinquency and how it’s either prevented, or how it’s remedial has not focused on school counselors' work. School is an area where children spend much of their time, it’s interesting to find out how the schools work to counteract this social problem. The aim of this study is to investigate how counselors at different schools in Malmö work with prevention and remedial measures against juvenile delinquency. We also intended to find out what opportunities and difficulties the counselors experienced in their work. This is a qualitative study based on six school counselors and their experiences. The data has been collected from interviews with the school counselors, and previous research regarding juvenile delinquency. The theories that were used to analyze the result are The social bond theory and the theory on Sense of coherence. The results from this study presented different risk and protective factors that school counselors mean is connected to the development of juvenile delinquency. The results also showed that there is no specific work description made for school counselors work with the problematic matter and therefore the preventive and remedial work depends on the school counselor, and varies a lot from school to school. The school counselors believe that trust building with the students is an effective approach to the matter

Development of optimum solar irradiation energy model for Iran

In this article, an optimal model for calculating the total solar irradiation is represented for Iran. Eight irradiation models are analysed based on the meteorology information of 22 synoptic stations. Afterwards, accuracy of these methods is compared using standard error criteria. Hence, Daneshyar and Modified Daneshyar are introduced as the most precise methods. Then, a new coefficient is added to Daneshyar model and Niroo Research Institute (NRI) model is presented. Ultimately, errors of NRI method are compared with other methods and it is observed that regarding all types of errors, NRI model has the most conformity with experimental data.cloud factor; diffused radiation; direct radiation; error analysis; Iran; irradiation modelling; meteorological data; optimum; solar energy; solar power; total radiation; total solar irradiation; Iran.

Performance Evaluation of a BESS Unit for Black Start and Seamless Islanding Operation

The main purpose of this paper is to evaluate the overall performance of a battery energy storage system (BESS) during I) grid‐connected, II) black start, and III) islanded operating modes. To do so, firstly, a novel three‐mode controller is proposed and developed. The proportional–integral–derivative (PID) controller is implemented, including the following three components: (1) inertia emulation, (2) frequency‐active power and voltage‐reactive power droops, and (3) secondary frequency and voltage controllers. Secondly, to effectively evaluate the proposed controller performance under various grid operating conditions during both black start and seamless transition to islanded operation, a set of comprehensive dynamic simulations using Matlab/Simulink is carried out. To this end, the sensitivity analyses on numerous grid operating parameters, such as pre‐disturbance grid power, total installed BESS capacity, battery state of charge, unbalanced three‐phase load flows, implemented power‐frequency controller parameters, and distribution network types with various shares of dynamic and static loads, are performed. Thirdly, to practically improve the seamless transition performance enabling the demand response participation, a fast‐controlled thermostatic load scheme is implemented. Simulation results show that the BESS unit using the proposed three‐mode controller has great potential to successfully control the frequency and voltage within allowable limits during both islanding and black start modes over a wide range of grid operating conditions.Electrical Engineering Educatio